Macroinvertebrates assemblages of high altitude lakes, inlets and outlets in the southern Alps

Abstract

The invertebrate fauna of 21 high altitude lakes on the southern side of the Alps (Italy and Switzerland) were sampled once in the 1990 s. A total of 193 taxa was identified in 48 samples: 66 taxa were exclusive to the littoral zone, 17 to the outlets and 23 to the inlets. Chironomids prevailed in all environments with few exceptions. Inlets and littoral zones proved to be the richest habitats in number of taxa, while the littoral zones were richest in number of individuals. In all, 17,778 individuals were found in the Pennine-Lepontine Alps and 1966 in the Rhaetian ones. The number of taxa was 108 and 122, respectively. 69 taxa were exclusive to the former and 83 to the latter. Four groups of lakes have been distinguished by DCCA analysis applied to the littoral chironomid community. Water temperature, altitude, hydrochemistry, and lake area were the abiotic variables mostly related to chironomid distribution. Many steno-thermal species, typical of oligotrophic waters and high mountain streams were found, such as Zavrelimyia punctatissima, Diamesa latitarsis gr., Orthocladius frigidus, Prosimulium latimucro, Dictyogenus fontium, Baetis alpinus and Crenobia alpina. Only a few taxa such as D. fontium, Halesus radiatus, Plectrocnemia conspersa, Heterotris-socladius marcidus, Ablabesmyia sp., and Procladius sp. appeared to be tolerant to acidic conditions. These findings, as well as the rarity of molluscs, indicated that these environments are slightly acidic or at risk of acidification. Further studies on macroinvertebrates are required if they are to be used as possible indicators of local and global changes (e.g. acid deposition) in remote regions.